Exploiting Oxytricha trifallax nanochromosomes to screen for non-coding RNA genes

Area of Science:

• Molecular Biology
• Genomics
• RNA Biology

Background:

• Ciliates possess a unique dual-nucleus system with a somatic macronucleus containing fragmented, single-gene nanochromosomes.
• This extreme genome organization in Oxytricha trifallax facilitates the isolation of genes, including non-coding RNA (ncRNA) genes.

Purpose of the Study:

• To leverage Oxytricha trifallax's genomic architecture for screening eukaryotic non-coding RNA (ncRNA) genes.
• To identify novel ncRNA genes and characterize their prevalence within the Oxytricha genome.

Main Methods:

• Utilized a draft Oxytricha genome assembly and a custom protein-coding gene-finding program.
• Identified nanochromosomes lacking protein-coding genes to enrich for ncRNA gene candidates.
• Screened for known ncRNA classes and novel small RNA families.

Main Results:

• A small proportion of non-coding nanochromosomes were identified, suggesting limited independent ncRNA genes beyond known types.
• Identified new members of known ncRNA classes, including C/D and H/ACA small nucleolar RNAs (snoRNAs).
• Discovered a novel family of small RNA genes, termed Arisong RNAs, exhibiting characteristics similar to small nuclear RNAs.

Conclusions:

• The study successfully screened for ncRNA genes in Oxytricha trifallax by exploiting its unique nanochromosome structure.
• The findings indicate a limited repertoire of independent ncRNA genes in Oxytricha, with the notable discovery of the Arisong RNA family.